SPAC demonstration

Grant Cramer cramer at med.unr.edu
Tue Dec 11 17:30:52 EST 2001


A word of caution: All of these demonstrations are useful but they don't
necessarily demonstrate how water moves up a TALL 100 m redwood. Capillarity
only works so far and I suspect these models have their limitations, too.


-- 
Grant R. Cramer
Associate Professor
Department of Biochemistry
Mail Stop 200
University of Nevada
Reno, NV 89557

Phone: (775) 784-4204
Fax: (775) 784-1650
Email: cramer at unr.edu
Web page: http://gcramer-mac.ag.unr.edu/index.html


on 12/11/01 1:17 PM, "Robinson, Dr. David" at drobinson at bellarmine.edu
wrote:

> 
> NEAT! Actually, if you just stacked the porous plate (simulating a leaf)
> on top of the porous rod (simulating a stem) that this company sells,
> assuming good contact between them, you might be able to create a
> "circuit" of water. Then if you placed it in a water:dye solution, the
> dye might be observed to travel up the rod, in time (especially, if you
> wrapped the rod in saran wrap).
> 
> Kind of depends on how expensive these ceramic products are, though, as
> I imagine the dye would probably never wash out!
> 
> Thanks for your detailed help!!
> 
> Dave Robinson, Bellarmine U.
> 
> -----Original Message-----
> From: dh321 at excite.com [mailto:dh321 at excite.com]
> Sent: Monday, December 10, 2001 9:52 PM
> To: plant-ed at net.bio.net
> Subject: Re: SPAC demonstration
> 
> The Soil Moisture Equipment Company -
> http://www.soilmoisture.com/ceramics.htm - sells a variety of porous
> ceramic
> products for tensiometers and other uses.
> 
> I looked back through a bunch of old plant physiology lab manuals on use
> of
> atmometers. They all used mercury which may not be acceptable to some
> today.
> However, without the mercury a major aspect of the demonstration is
> lost.
> With modern materials such as narrow-bore plastic tubing, perhaps it
> would
> be possible to create a much taller atmometer demonstration with water
> instead of mercury.
> 
> Oels (1894) early atmometer used a thistle tube with a pig bladder or ox
> 
> bladder stretched over the opening instead of an porous clay cup. He
> could
> raise mercury 20 cm with a pig bladder and 30 cm with an ox bladder.
> 
> MacDougal (1895) reported that active coniferous shoots, in place of a
> porous clay cup, could raise mercury 76 cm high.
> 
> Lemon (1958) noted that the atmometer is a "a classic experiment
> ...difficult to carry out" and noted the importance of recently boiled
> distilled water, super clean glassware, and eliminating all air bubbles.
> He
> mentioned that this was Askenasy's experiment. The porous clay cups he
> also
> called Livingston atmometers. Lemon (1958) also has an exercise
> demonstrating capillary rise with panes of glass and capillary tubes
> 0.05 to
> 3 mm in diameter.
> 
> Meyer et al. (1955) gave a detailed description of the atmometer setup
> saying a 1 meter-plus length of 1 mm bore glass capillary tube should be
> 
> used with a porous porcelain cylinder. Their drawing of the porous
> porcelain
> cylinder looked like a tensiometer tip. They suggested coating the
> porous
> cylinder with a hot 20% gelatin sol "to permit attainment of
> satisfactory
> results with cups which otherwise could not be used."
> 
> Witham et al (1971) adapted the experiment of Meyer et al. (1955) but
> cited
> Askenasy's 1896 papers in German. They also gave the source for the
> porous
> clay cups as Mrs. Burton E. Livingston, Sherwood Ave., Riverwood,
> Baltimore,
> MD. but I doubt that source is still valid.
> 
> The latest three manuals all cite Thut (1932) but I have not seen that
> article.
> 
> References
> 
> Lemon, C. Paul. 1958. Laboratory Exercises Plant Physiology. Dubuque,
> IA.
> Wm. C. Brown.
> 
> MacDougal, Daniel T. 1895. Practical Text-book of Plant Physiology. New
> York: Longmans Green.
> 
> Meyer, Bernard S., Anderson, Donald B., and Swanson, Carroll A. 1955.
> Laboratory Plant Physiology. Princeton, NJ: D. Van Nostrand.
> 
> Oels, Walter. 1894. Experimental Plant Physiology. Mineapolis: Morris
> and
> Wilson.
> 
> Thut, H.F. 1932. Demonstrating the lifting power of transpiration. Amer.
> J.
> Botany 19:358-364.
> 
> Witham, Francis H., Blaydes, D.F. and Devlin R.M. 1971. Experiments in
> Plant
> Physiology. New York: Van Nostrand Reinhold.
> 
> 
> 
> 
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